1. Field of the Invention
The present invention relates to a cyclic amide derivative and a pharmaceutical agent containing the cyclic amide derivative as the effective ingredient. More specifically, the invention relates to a cyclic amide derivative useful as a therapeutic drug or preventive drug of arthritis and rheumatism due to the increase of bone resorption in addition to bone diseases such as osteoporosis, hypercalcemia, and Paget's disease.
2. Discussion of Background
Following the rapid progress of the phenomenon of aging society in recent years, the frequencies of senile diseases are increased due to the increase of aged people, causing a serious social problem. The number of patients with bone diseases in particular is increasingly elevated; among them, osteoporosis affects over 200 million people worldwide and postmenopausal osteoporosis affects 150 million people worldwide.
Postmenopausal osteoporosis is a serious problem; osteoporosis is observed in about 13% of females of age 40 years or older and in about 60% of females of age 60 years or older. The increase of bone resorption in menopausal female due to hormone imbalance or aging phenomenon is in close relation with the onset and progress of bone diseases, so bone resorption inhibitors are generally used for pharmaceutical treatment of such osteoporosis. However, pharmaceutical agents including calcitonin formulation, estrogen formulation, vitamin K formulation and bisphosphonate formulation and exerting an action to inhibit bone resorption have drawbacks in terms of the therapeutic effects, long lasting effects, side effects, drug compliance and the like. Hence, desirably, a bone resorption inhibitor functioning as a more highly effective therapeutic drug or preventive drug of osteoporosis will be developed.
Bone serves as a reservoir of an enormous amount of calcium in living organisms and calcium in bone is in equilibrium with calcium in blood; accordingly, calcium is consistently transferred from bone into blood or from blood into bone. Such calcium transfer between bone and blood is progressed in dynamic equilibrium between bone generation and bone resorption.
At the process of bone resorption, activated osteoclast dissolves inorganic bone materials such as calcium and concurrently degrades organic bone materials such as collagen. Recent research works indicate that cysteine protease secreted from osteoclast is responsible through collagen decomposition for bone resorption.
A report tells that in the lysosome of osteoclast are present cysteine proteases such as cathepsin B, cathepsin H, cathepsin L and cathepsin S and that inhibitors of these cysteine proteases exert an action to inhibit bone resorption (Biochem. J., 192, p.365 (1993); Biochem. Biophys. Res. Commun., 125, p.441 (1984); FEBS Lett., 321, p.247 (1993); JP-A-8-92193; JP-A-8-41043; JP-A-7-101924; JP-A-5-155764).
More recently, human cathepsin K locally present in osteoclast has been isolated. It has been elucidated that the expression thereof in osteoclast is greater than the expression of other cathepsins [Biochem. Biophys. Res. Commun., 206, p.89 (1995); J. Biol. Chem., 271, p.12511 (1996)]. Furthermore, it is suggested that patients with pycnodysostosis causing abnormality in bone resorption are mutant cathepsin K gene [Science, 273, p.1236 (1996)]. As has been described above, cathepsin K is drawing attention as a cysteine protease principally involved in bone resorption. Thus, it is expected that a cathepsin K inhibitor may function as a bone resorption inhibitor.
As compounds with cathepsin K inhibitory action, conventionally, aldehyde derivatives or epoxysuccinic acid derivatives [J. Biol. Chem., 271, p.2126 (1996); Biol. Pharm. Bull., 19, 1026(1996)] or vinylsulfone derivatives [Nature Structural Biology, 4, 105 (1997); J. Med. Chem., 38, 3193 (1995)] have been reported, but it is known that these derivatives are so poorly selective that these strongly inhibit cysteine proteases such as cathepsin B, cathepsin H, cathepsin L, cathepsin S and calpain, other than cathepsin K [J. Enzyme Inhibition, 3, p.195 (1990); Biochem. Biophys. Res. Commun., 153, p.1201(1988); J. Biochem., 87, 339(1980); J. Biochem., 88, p.1805 (1980)].
While attention has been focused on cathepsin K as described above, furthermore, active research works have been carried out on X-ray crystallography of cathepsin K and inhibitors thereof [Nature Structural Biology, 4, 105 (1997); Nature Structural Biology, 4, 109 (1997)]. Consequently, a compound with an action selectively inhibiting cathepsin K has been known [Proc. Natl. Acad. Sci. USA, 94, 14249 (1997); WO 9801133; J. Am. Chem. Soc., 120, 9114 (1998); J. Med. Chem., 41, 3563 (1998)]. WO 9716177 describes the active site of cathepsin K and discloses the method for inhibiting cathepsin K by using a compound interactive with the active site.
While the compounds inhibiting cathepsin K have been drawing attention as bone resorption inhibitors as described above, numerous derivatives thereof have been reported, none of them has been practically applicable as a therapeutic drug of metabolic bone diseases.
Characteristic properties demanded for such therapeutic drug include therapeutic efficacy, long lasting effect, safety profile, and whether or not oral dosing is possible. Because the patients are older so therapeutic drugs therefor are possibly administered for a long term, significantly, these drugs should be clinically effective when dosed orally.
Thus, it is an object of the invention to provide a novel derivative functioning as a bone resorption inhibitor with a strong and selective inhibitory action of cathepsin K and with an efficacy when dosed orally.